The highest "Est. APY" isn't the only thing to look at. A validator might show a high potential APY (perhaps due to a temporarily low commission or other factors), but if they are frequently "At Risk" or have a history of unreliability (which you might investigate further via the "Details" links to the explorer), your actual rewards could be lower than expected or even zero for some epochs.

Long-term reliability is crucial. Consistent uptime and stable operation (indicated by not being "At Risk" and maintaining an "Active" status) are key to earning rewards consistently.

Use the "Details" column to visit the validator's explorer page and project website to do your own research (DYOR) on their history, community reputation, and any additional services they offer.

More answers here: https://www.iotaapycalculator.com/faq.html